The present invention relates to an exposure time control circuit of an electric shutter for a camera using a digital memory and read out system. The present invention especially relates to improvements for the type circuit in which the memory value to be counted in a counting circuit exceeds the capacity of the counting circuit.
Known electric shutter control circuits use a digital memory counting and read out system so arranged that standard pulses are counted and memorized in the counting circuit during the generation of a single pulse with a pulse width representative of the brightness of a subject to be photographed. This system cannot continue to count pulses where the memory value rises above the maximum capacity of the counting circuit. In this device, the photographic limits are determined by the memory capacity of the counting circuit, and to increase the memory capacity of the counting circuit in consideration of an exposure time of hours, the number of counting stage of the counting circuit must be increased, and therefore, that results in increased cost as well as complication of the circuit.